WAN<->LAN bridge (sort of)?

[clarknova]

I don't know why I'm having trouble wrapping my head around this, but I need some advice.

I have an mlppp connection, and a single host that needs a static IP. Basically, I'm brokering the connection to relieve a Cisco host of the need to do mlppp.

Everybody likes a diagram:

Internet
   
<mlppp>pfsense <lan>
                      Cisco

I need to be able to assign the Cisco a static, publicly routable IP (or have it assigned via dhcp).

I'm confident I could get a static IP on pfsense's WAN and a /29 public subnet on the LAN, from which to assign 1 address to pfsense's LAN interface, and 1 to the Cisco, but renting 5 IP addresses just to use 1 is wasteful. What I'm trying to figure out is if I can do it with less, but I don't see that as an option. It seems that if I bridge WAN to LAN then I've passed on the need to do mlppp to the Cisco and defeated myself, right?

Alternatively, I could use 1:1 NAT and assign a private address to the Cisco, but I don't think that will be acceptable; ultimately I think I will need a public IP address there.

Am I missing an option, or is static+subnet the only way to accomplish this?

Thanks for looking.</lan></mlppp>

[cmb]

@clarknova:

It seems that if I bridge WAN to LAN then I've passed on the need to do mlppp to the Cisco and defeated myself, right?

Probably, your ISP likely assigns your one public IP to your MLPPP, hence whatever needs that public IP will have to do the MLPPP. Otherwise maybe they can route a single public IP to you in addition to that.

[clarknova]

Ok, thanks. And oops, yeah, I meant /30 subnet on the LAN, not that it matters.

[cmb]

Yeah they probably wouldn't route a single public IP to you (though they could and you could make it work that way, it's kinda ugly), probably be a /30.